Evaluate > Mass properties

To display mass properties

Display mass properties (volume, surface area, centroid) of a model.

The Mass properties tool provides two ways of specifying the object to measure:

Solid: the surfaces you pick represent the boundaries of a closed, solid object.
Shell Interior: the surfaces you pick represent the outside of a thin shell enclosing a hollow space (e.g. modeling a bottle with a single surface of revolution). You specify the thickness of the shell.

Restrictions

To get accurate statistics on an object, the following conditions must be met:

The surfaces must completely enclose a volume. The edges of surfaces must meet within the tolerance value set in the Mass properties option window.
The normals on all NURBS surfaces must point out of the solid, and, when moving along a face boundary in the increasing U direction, the face area must be to the left when viewed from outside the solid.
or

The normals on all NURBS surfaces must point into the solid, and, when moving along a face boundary in the increasing U direction, the face area must be to the right when viewed from outside the solid.

You can check the seam between two surfaces by placing a Deviation measurement on the seam. You can check the orientation of normals using the Reverse direction tool.

Display

The Mass properties window displays the following information:

Label	Description	Formula
Units	Current unit of measurement (default is either centimeters or millimeters, depending on which product you are using).
Area	Area of the picked surfaces.
volume	Volume enclosed by the picked surfaces, or volume occupied by shell surface with given thickness.
centroid	X, Y, Z coordinates of the center of the object

NoteIf you are using a construction plane when you click the tool, the calculations use the X, Y, and Z axes of the current construction plane.

To show the mass properties of a model

Pick all the surfaces that make up the model. Make sure the surfaces completely enclose the volume of the object.
Click the Mass properties icon, or choose Mass properties from the Evaluate palette menu.
When the Mass properties tool completes its calculations, the Mass properties window appears, containing statistics about the object.

If you change the options of the Mass properties tool, the window will update.

Tips and notes

Using the Mass properties tool with the Solid option on a group of surfaces with gaps will not produce an error.
In fact, the results are still meaningful if the gaps between surfaces are not too large.
If the volume value is negative, some of the surfaces probably have normals pointing inward. Use the Surface Edit > Orientation > Reverse Surface Orientation tool or Surface Edit > Orientation > Set Surface Orientation to find and reverse the surfaces so they have normals pointing out.

Options

Volume, Surface Area, Centroid: Check the values you want to display in the Mass properties window.
Type: Describe the way the selected surfaces or faces define the solid.

Solid: the surfaces you pick represent the boundaries of a closed, solid object.

Shell Interior: the surfaces you pick represent the exterior of a thin shell enclosing a hollow space (e.g. modeling a bottle with a single surface of revolution). The Thickness option (below) specifies the thickness of that shell.
Tolerance: The maximum distance allowed between adjacent surfaces for them to form a closed volume
Thickness: The uniform thickness of the shell when using the Shell Interior option (above). In this case, the Volume corresponds to the volume of the shell, rather than that of the enclosed space. The Surface Area corresponds to the sum of the interior and exterior surface areas.

This option appears only when Shell Interior is turned on.

Buttons

Extract to File: Click this button to save the mass properties data to a text file.